Back to EveryPatent.com
United States Patent |
5,733,212
|
Wise
,   et al.
|
March 31, 1998
|
Electronic racket stringing machine
Abstract
A racket stringing machine consists of a racket cradle assembly, to lock a
racket frame in place, and a tension head assembly to grip and apply
tension to the string during the stringing or restringing process. During
the process an electronically controlled, motor-driven assembly holds the
loose end of the string and applies tension as it guides it in its motion
away from the racket frame. Electronics compare at each instant the
tension on the string to a previously dialed-in one and when both are
equal the carriage halts.
Inventors:
|
Wise; Herbert H. (Los Angeles, CA);
Calia; James A. (Oxnard, CA)
|
Assignee:
|
Wise U. S. A., Inc. (Los Angeles, CA)
|
Appl. No.:
|
727113 |
Filed:
|
October 8, 1996 |
Current U.S. Class: |
473/557 |
Intern'l Class: |
A63B 051/14 |
Field of Search: |
473/553,555,556,557
|
References Cited
U.S. Patent Documents
1969826 | Aug., 1934 | Tauber et al.
| |
2067512 | Jan., 1937 | Sterns.
| |
2114216 | Apr., 1938 | Doll.
| |
2154870 | Apr., 1939 | Serrano.
| |
2188250 | Jan., 1940 | Serrano.
| |
3441275 | Apr., 1969 | Held.
| |
3635080 | Jan., 1972 | Krueger et al.
| |
3918713 | Nov., 1975 | Kaminstein.
| |
3964291 | Jun., 1976 | Ogden.
| |
4125259 | Nov., 1978 | Halbrook | 473/557.
|
4348024 | Sep., 1982 | Balaban.
| |
4366958 | Jan., 1983 | Bosworth.
| |
4376535 | Mar., 1983 | Muselet et al.
| |
4417729 | Nov., 1983 | Morrone.
| |
4546977 | Oct., 1985 | Bosworth, Jr. et al.
| |
4590808 | May., 1986 | Lightfoot et al.
| |
4593905 | Jun., 1986 | Abel | 473/556.
|
4620705 | Nov., 1986 | Tsuchida.
| |
4706955 | Nov., 1987 | Ngadi et al. | 473/556.
|
4864875 | Sep., 1989 | Wise.
| |
4878170 | Oct., 1989 | Zech.
| |
5026055 | Jun., 1991 | Longeat.
| |
5080360 | Jan., 1992 | Longeat.
| |
5090697 | Feb., 1992 | Lee.
| |
5186505 | Feb., 1993 | Chu.
| |
5269515 | Dec., 1993 | Chu.
| |
Primary Examiner: Stoll; William E.
Attorney, Agent or Firm: Mitchell, Silberberg & Knupp LLP
Claims
What is claimed is:
1. A tension head assembly comprising:
a snatch vice for engaging a racket string; and
a motor drive screw assembly operatively connected to said snatch vice such
that the snatch vice is movable in a direction away from a racket thereby
creating tension in a string.
2. The tension head assembly of claim 1 wherein the motor drive screw
assembly comprises a lead screw and nut coupled to a reversible, electric
motor.
3. The tension head assembly of claim 2 wherein the motor is controlled by
a motor controller assembly which accepts input from a strain gauge.
4. The tension head assembly of claim 3 wherein the circuitry of said motor
controller assembly is temperature compensated.
5. The tension head assembly of claim 3 wherein said motor controller
assembly provides the operator the option either to halt the motor with
pull and brake or to apply constant pull to the string.
6. The tension head assembly of claim 3 wherein the motor controller
assembly accepts input from the operator to vary the speed of the motor.
7. The tension head assembly of claim 3 wherein the number of full cycle
repetitions of applying and then releasing tension from the string are
counted and displayed.
8. The tension head assembly of claim 3 wherein the tension is displayed.
9. The tension head assembly of claim 8 wherein the operator has the option
to choose a tension reading in pounds or kilograms.
10. A racket stringing machine comprising:
a base;
a racket cradle assembly supported by the base;
a tension head bar extending outwardly from the base; and
a tension head assembly supported by and connected to the tension head bar,
said tension head assembly comprising:
a snatch vice for engaging a racket string; and
a motor drive screw assembly operatively connected to said snatch vice such
that the snatch vice is movable in a direction away from a racket thereby
creating tension in a string.
11. The racket stringing machine of claim 10 wherein the motor drive screw
assembly comprises a lead screw and nut coupled to a reversible, electric
motor.
12. The racket stringing machine of claim 10 wherein the motor is
controlled by a motor controller assembly which accepts input from a
strain gauge.
13. The racket stringing machine of claim 12 wherein the circuitry of said
motor controller assembly is temperature compensated.
14. The racket stringing machine of claim 12 wherein said motor controller
assembly provides the operator the option either to halt the motor with
pull and brake or to apply constant pull to the string.
15. The racket stringing machine of claim 12 wherein the motor controller
assembly accepts input from the operator to vary the speed of the motor.
16. The racket stringing machine of claim 10 wherein the number of full
cycle repetitions of applying and then releasing tension from the string
are counted and displayed.
17. The racket stringing machine of claim 10 wherein the tension is
displayed.
18. The racket stringing machine of claim 17 wherein the operator has the
option to choose a tension reading in pounds or kilograms.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to tennis racket stringing machines.
2. The Prior Art
Many machines have been devised for stringing and restringing game rackets,
such as those used for tennis, badminton, squash and the like.
After 1969, a process that had previously been done by guess, intuition or
the displacement of fixed weights (Serrano, U.S. Pat. No. 2,188,250)
became more efficient and precise by using the compression of a spring
with its inherent linearity (Held, U.S. Pat. No. 3,441,275) as a
comparator. Here the stringing machine FIG. 15 holds the racket in a
cradle in a position parallel to the ground 130. The person stringing a
racket threads the string through a hole in the racket frame, attaching
one end to the racket and the other to an external self-tightening vise
131(snatch vise). The vise is part of a hand cranked tensioning assembly
132 (tension head) that automatically brakes when the tension on the
string equals the tension preset on a helical bias spring. The tension
head runs on a track 133 that draws the string away from the racket while
tensioning. This is the so-called Pull and Brake method.
Modified, Held's device is still used universally although its accuracy is
often called into question, its resolution is limited and it needs
frequent calibration. In substantially similar forms this machine is
manufactured by Ektelon, Gamma, Alpha, Czech Sports, Eagnas, Toalson,
Gossen, Kennex, Winn and others.
From 1975, machines surfaced that used electric motors to replace the hand
crank that compresses the bias spring (Kaminstein, U.S. Pat. No.
3,918,713), (Tsuchida, U.S. Pat. No. 4,620,705) and (Muselet et al., U.S.
Pat. No. 4,376,535).
Some machines used hydraulics or pneumatic systems as the power source
(Morrone, U.S. Pat. No. 4,417,729).
When wooden rackets became obsolete, rackets of aluminum, graphite, boron,
ceramic, Kevlar, etc. made their appearance along with hundreds of kinds
of new strings made of different plastics and multi-layered filaments.
Improvements to the equipment required an improvement in the accuracy of
the tools needed for their stringing and thus electronic machines.
Babolat of France (U.S. Pat. No. 5,026,055) and Poreex of Taiwan (U.S. Pat.
No. 5,090,697) manufacture essentially duplicate electronic machines sold
under their own name and brand labeled for others. In their device the
snatch vise is driven by a spring-loaded chain drive.
Not unlike earlier machines the chain drive compresses a helical spring.
Running parallel to this bias spring is a linear potentiometer. The
electronics read the linear potentiometer as it measures the spring
compression and indirectly the tension on the string through the
intermediary of the chain/spring/potentiometer assembly.
All electronic machines are "Constant Pull" machines and continue to apply
tension even after the dialed-in tension is reached because strings lose
some tension seconds after their initial pull. This Constant Pull feature
is often the cause of undesirable results. Knowledgeable players ask their
stringer which machine will be used to string their racket, mechanical
(Pull and Brake) or electronic (Constant Pull). The results can be
substantially different. Electronic machines will invariably produce a
racket that is 5-10 percent tighter (where it appears as if more tension
has been applied to the strings) than a Pull and Brake machine.
Professional players claim they can feel the difference in small fractions
of a pound.
SUMMARY OF THE INVENTION
As can be seen, both mechanical and electronic machines read the applied
tension to the racket string indirectly, that is, as a relationship to a
bias spring. It is the objective of this device to read the tension
applied to the racket string directly and consequently more accurately.
It is further the objective to use this tensioning device to replace the
mechanical tension heads currently used on mechanical machines.
It is further the objective to simplify any such device, to make it
transportable, to make it more durable, less complicated and easier to
repair if need be.
Also, the objective is to display digitally, the input value of the
tensioning device and to report with error codes any irregularities the
electronics may uncover.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view in perspective of the applicant's stringing machine;
FIG. 2 is a view in perspective of the tension head enclosure and keypad;
FIG. 3 is a view in perspective of the tension head assembly, opened;
FIG. 4 is a view in perspective of the snatch vice;
FIG. 5 is a view in perspective of the brace and flange;
FIG. 6 is a block diagram of the electronic controller assembly;
FIG. 7 is a view of the keypad;
FIG. 8 is the display circuit schematic diagram;
FIG. 9 is the keypad circuit schematic diagram;
FIG. 10 is the microprocessor circuit schematic diagram;
FIG. 11 is the motor controller circuit schematic diagram;
FIG. 12 is the strain gauge circuit schematic diagram;
FIG. 13 is the power supply circuit schematic diagram;
FIG. 14 is the LED/beeper circuit schematic diagrams; and
FIG. 15 is a view in perspective of a conventional mechanical stringing
machine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a view of applicant's stringing machine with its two major
components, the racket cradle assembly 1 and the tension head assembly 2.
The stringing machine has a base 3 including legs 4, 5, 6 and 7 spaced
from each other at 90.degree. degrees. The base also includes a vertical
support column 8, on top of which is fitted the racket cradle assembly
tension bar 9. Mounted on the support column and above the tension bar is
the racket cradle assembly which takes the form of a turntable. Both the
tension bar and the racket cradle assembly pivot on the support column so
that when a racket is mounted onto the cradle, as we will see, the string
can be aligned from the point it leaves the racket frame to where it
enters the snatch vice 80.
The racket cradle assembly platen 10 has two functions; to support four
movable posts or fixing elements 11, 12, 13 and 14 that are placed at the
top, bottom and two sides of the racket and ensure the horizontal clamping
in position of the tennis racket to be strung. The elements 11, 12, 13 and
14 are arranged in exactly the same way so it is sufficient to describe
only one of them, for example fixing element 11. The fixing element 11 is
grooved 15 and fitted with a non-skid surface to grasp the tennis frame
firmly.
The elements are arranged and fixed to the racket cradle platen, opposite
one another about the longitudinal axis of the racket cradle, which
corresponds to the axis of symmetry of the racket. The elements are
adjusted to accept any size racket by moving their supporting bracket, and
when pressed against the outer wall of the racket frame support the frame
from distortion during the stringing process. Once the four fixing
elements support the racket the elements are firmly locked into place. The
racket cradle assembly platen also supports two string clamps 16. These
clamps move freely on the racket cradle platen through slots in the platen
but once they are appropriately positioned to hold the string a single
motion of the lever arm 17 locks the string in the clamp and firmly seats
the clamp onto the platen. One of the clamps holds the racket end of the
string while the loose end of the string is being tensioned by the tension
head assembly. Once the string is tensioned the second clamp holds the
string under tension. The process is repeated after the racket is rotated
180.degree. degrees and the loose end of the string is woven anew into the
next hole in the racket frame.
The particular design of the racket cradle is not important to the present
invention and the racket cradles in the following United States patents
can be used as part of the present invention: (1) U.S. Pat. No. 5,090,697
on Racket Frame Stringing Machine issued to Lee on Feb. 25, 1992; (2) U.S.
Pat. No. 5,080,360 on Equipment For Stringing A Tennis Racket issued to
Longeat on Jan. 14, 1992; (3) U.S. Pat. No. 5,186,505 on Chucking Device
Of Racket Stringing Machine issued to Chu on Feb. 16, 1993; (4) U.S. Pat.
No. 5,026,055 on Equipment For Stringing A Tennis Racket issued to Longeat
on Jun. 25, 1991; (5) U.S. Pat. No. 4,874,170 on String Clamp For Racquet
Stringing Machine issued to Zech on Oct. 17, 1989; (6) U.S. Pat. No.
4,620,705 on Racket Stringing Device issued to Tsuchida on Nov. 4, 1986;
(7) U.S. Pat. No. 4,417,729 on Racket Stringing Apparatus issued to
Morrone on Nov. 29, 1983; (8) U.S. Pat. No. 4,546,977 on Racquet Stringing
Machine With Improved Racquet Retaining Standard issued to Bosworth, Jr.
et al., on Oct. 15, 1985; (9) U.S. Pat. No. 4,376,535 on Machine For
Stringing Rackets issued to Muselet et al., on Mar. 15, 1983; (10) U.S.
Pat. No. 4,366,958 on Racket Stringing Machines issued to Bosworth on Jan.
4, 1983; (11) U.S. Pat. No. 4,348,024 on Racket Stringing Apparatus And
Method issued to Balaban on Sep. 7, 1982; (12) U.S. Pat. No. 3,918,713 on
Racket Stringing Machine issued to Kaminstein on Nov. 11, 1975; and (13)
U.S. Pat. No. 3,441,275 on Racket Stringer issued to Held on Apr. 29,
1969. The specifications and drawings of each of these 13 listed United
States Patents are hereby incorporated herein as though set forth in full.
FIG. 2 is a perspective view of the tension head enclosure showing the
display window 20 the keypad area 21, the enclosure stand 43 and the brace
62. The keypad is shown in FIG. 7.
FIG. 3 is a perspective view of the tension head assembly. The tension head
assembly 40 consists of four assemblies; the motor drive screw assembly
with gear motor 51, lead screw 52 (other types of ball screws can be
used), coupler 53 and bearing 54 and the screw nuts 55; the snatch vise
cradle assembly with the snatch vise 61(not shown here), brace 62 with the
attached strain gauges 63, the left and right flanges 64, and the left and
right nuts 55; the electronic controller assembly; and the tension head
enclosure 41 and back cover assembly 42. Four screws 73 secure the tension
head enclosure back cover to the tension head enclosure. In FIG. 3 the
snatch vise assembly is shown twice, in its forward 70A and its retracted
positions 70B. The tension head assembly stand 43 is mounted with four
bolts onto the racket cradle assembly tension bar 9 and allows for height
alignment of the tension head with various types of racket cradle
assemblies.
The gear motor (preferably a DC motor) and its drive shaft are mounted
longitudinally, with the motor gearbox secured to the tension head
enclosure inner wall. The coupler is located on the end of the motor drive
shaft.
The lead screw 52 is connected to the motor drive shaft via the coupler 53.
The coupler has two set screws to secure the end of the lead screw to the
end of the motor drive shaft. The opposite end of the lead screw is slid
into the bearing 54. Said bearing is located in a recess within the
enclosure wall 57 closest to the racket cradle assembly.
FIG. 4 shows the snatch vice 80. The lower half of the snatch vise contains
an opening which is slightly wider than the thickness of the brace. The
top of the brace FIG. 5, 91 fits within said opening where the three holes
81 in the top of the brace align with the three holes in the lower half of
the snatch vise and is secured to the top of the brace by three bolts 87.
Onto the brace are mounted the compression strain gauge and the tension
strain gauge FIG. 5.
Two sets of grooves in each outer wall 82 correspond to similar grooves in
the two jaws 83. The two jaws slide within the outer walls on ball
bearings 84, are aligned to each other by pins 85 and held apart with
small internal springs 86. The depth of the groves in the walls and jaws
vary from one end of the groove to the other. At the point where the
grooves are deepest the jaws remain farthest apart as the springs force
the jaws open allowing the loose end of the string to be inserted between
the jaws. The jaws become a self-closing vice as soon as tension is
applied to the string because the grooves become shallower at the front
end of the snatch vise and the jaws close as they are motor driven away
from the racket cradle.
Turning back to FIG. 3, the right flange is aligned, just beneath the
brace, on the right side of the brace. The top of the right flange
contains a tapped hole (FIG. 5 88) which aligns with a through hole in the
right side of the brace. A bolt secures the right flange to the right side
of the brace. The left flange is attached to the left side of the brace in
a similar manner. Both flanges are secured perpendicular to the brace and
parallel to each other. The right nut contains both inner threads and
other threads. The outer threads of the right nut match the inner threads
of the right flange. The right nut is screwed into the right flange, with
the unthreaded portion of the right nut outer thread under the brace. The
left nut is secured to the left flange in a similar manner. The inner
threads of both the right and left nuts match the thread of the lead screw
of the motor drive screw assembly.
The snatch vise carriage assembly is connected to the motor drive screw
assembly by screwing the lead screw, of the motor drive screw assembly
into both nuts of the snatch vise carriage assembly. The snatch vise
carriage assembly is thus allowed to translate the length of the lead
screw in both directions by applying a positive or a negative voltage to
the gear motor.
The sides of the brace of the snatch vise carriage assembly align with the
walls of the tension head enclosure and the tension head enclosure back
cover. Said walls prohibit the snatch vise carriage assembly from any
rotational motion, while allowing the snatch vise carriage assembly to
translate in the direction parallel to the racket cradle assembly tension
head bar.
As shown in FIG. 5 the compression strain gauge 95 is attached by an
adhesive to the vertical wall 96 of the brace parallel and furthest from
the motor gear box. The tension strain gauge 97 is attached to the
opposite wall 98 of the brace directly behind the compression strain
gauge, in a similar manner.
FIG. 6 is a block diagram showing the control operation of the present
invention. Output from the compression and tension strain gauges 100 is
input into a strain gauge bridge circuit 101. Output from the strain gauge
bridge circuit is input into a microprocessor circuit 102. The
microprocessor circuit also receives input from a carriage position
detection circuit 103 and a keypad circuit 104, and which receives input
from an electronic keypad 105. The microprocessor circuit outputs to an
LED display circuit 106 such that the tension reading from the compression
and tension strain gauges is displayed and also provides input into motor
drive circuit 107 which in turn operatively controls a gear motor 108.
The electronic controller assembly consists of the electronic controller
circuit board onto which is mounted the electronic keypad 120 in FIG. 7.
The electronic controller circuit board is mounted inside the tension head
enclosure, just behind the tension head enclosure display window opening.
The electronic controller circuit consists of the following sub circuits;
the strain gauge bridge sub circuit, FIG. 12, the keypad sub circuit, FIG.
9, the motor controller sub circuit, FIG. 11, the LED driver sub circuit,
FIG. 14, the microprocessor sub circuit, FIG. 10, the power supply sub
circuit, FIG. 13 and the display sub circuit, FIG. 8.
As shown in FIG. 12, the strain gauge bridge sub circuit consists of the
following components; the whetstone bridge, the operational amplifier 221,
and the analog to digital converter 222. Both the compression strain gauge
223 and the tension strain gauge 224 are connected to the electronic
controller circuit board (preferably by a five conductor shielded cable
with twisted pairs such that one of the twisted conductor pairs is
connected to the two legs of the compression strain gauge, the other of
the twisted conductor pairs is connected to the tension strain gauge and
the shield of the said cable is connected to ground on the electronic
controller circuit board). One leg of the compression strain gauge is
connected to the whetstone bridge reference voltage, while the other leg
of the compression strain gauge is connected to both the positive input of
the operational amplifier and one leg of the tension strain gauge. The
other leg of the tension strain gauge is connected to ground. Thus the two
strain gauges make up one side of the whetstone bridge circuit.
Two temperature match resistors are connected accordingly to form the other
side of the whetstone bridge circuit. With the node connecting said
resistors also connecting to the negative input of the operational
amplifier.
The operation of the strain gauge bridge circuit is as follows. When a
longitudinal force is exerted on the snatch vise, in a direction towards
the racket cradle, a bending moment is experienced by the brace. This
bending moment will create a compression strain along the surface of the
brace where the compression strain gauge is located. Said bending moment
will, at the same time, create a tension strain along the surface of the
brace where the tension strain gauge is located. When the compression
strain gauge experiences compression strain, the resistance of the
compression strain gauge decreases proportionally to the force exerted on
the snatch vise. When the tension strain gauge experiences a tension
strain, the resistance of the tension strain gauge increases
proportionally to the force exerted on the snatch vise. When the
resistance of the compression strain gauge decreases while the resistance
of the tension strain gauge increases, the voltage at the node connecting
the two strain gauges, increases with respect to the voltage at the node
connecting the resistors of the bridge together. The difference in the
voltage at the two bridge nodes is known as the bridge output voltage 220.
The bridge output voltage increases proportionally with the force exerted
on the snatch vise. The compression strain gauge and the tension strain
gauge are temperature matched, their change in resistance with temperature
are the same. The two bridge resistors are also temperature matched.
Therefore any resistance change in the strain gauges, due to temperature
change, will be exactly the same, thus the voltage at the node where the
two strain gauges are connected will not vary with change in temperature.
Any resistance change in the two bridge resistors resistances, due to
temperature, will also be the same, thus the voltage at the bridge node
connecting the two bridge resistors together will not vary with
temperature. The bridge output voltage, which is the difference in the two
node voltages of the bridge, also will not vary with change in
temperature. Therefore the bridge output voltage is temperature
independent.
The bridge output voltage 220 is fed into the operational amplifier 221
which amplifies it and feeds it to the analog to digital converter 222.
The analog to digital converter converts the operational amplifier's
output voltage to a 14 bit digital numerical representation. This 14 bit
digital numerical representation is known as the bridge.sub.-- strain.
The value of the bridge.sub.-- strain is directly proportional to the force
exerted on the snatch vise. The analog to digital converter is connect to
the microprocessor circuit via a digital interface over which the
bridge.sub.-- strain value is passed to the microprocessor circuit FIG.
10.
The motor controller circuit FIG. 11 is driven by a digital interface with
the microprocessor circuit. The motor controller circuit provides power to
the gear motor. A two conductor cables connects the gear motor to the
electronic assembly circuit board. The motor controller circuit can
provide four combinations of power to the gear motor. The motor controller
can provide a positive voltage to the gear motor, which will cause the
gear motor to turn in a clockwise direction, which causes the lead screw
to rotate in a clockwise direction, which in turn causes the snatch vise
carriage assembly to translate in a direction away from the racket cradle.
The motor controller can also provide a negative voltage to the gear
motor, which causes the motor to turn in a counter clockwise direction,
which caused the lead screw to rotate in a counter clockwise direction
which in turns causes the snatch vise carriage assembly to translate in a
direction toward the racket cradle.
The motor controller can also provide a neutral voltage to the gear motor
where a neutral voltage is defined as applying the same positive voltage
to both leads of the gear motor. Applying a neutral voltage to the gear
motor locks the motor in its current position, causing the gear motor to
resists any torque placed on it by the lead screw via a longitudinal force
exerted on the snatch vise carriage assemble, essentially locking the
snatch vise carriage assembly in place.
The motor controller circuit can also place no voltage on the gear motor.
No voltage corresponds to placing zero volts on both leads of the gear
motor. Placing no voltage on the gear motor allows the gear motor to turn
when a torque is applied to the drive shaft via the lead screw, when a
longitudinal force is exerted on the snatch vise carriage assembly, thus
allowing the snatch vise carriage assemble to translate when a
longitudinal force is exerted on the snatch vise.
The electronic keypad consists of a switch matrix with eleven switches,
five LEDs and a ribbon cable. The ribbon cable connects the electronic
keypad to the electronic assembly circuit board. The electronic keypad
switch matrix consists of four scan lines and four read lines, where a
particular scan line is connected to a particular read line when a
particular switch is closed. The four scan lines and four read lines are
connected to the keypad circuit. The keypad circuit sequentially places a
voltage on one and only one of the scan lines at a time, and then checks
the four read line for said voltage. The keypad circuit sequences through
all four scan lines, before repeating the cycle. If a particular switch is
pressed, the keypad circuit passed the particular switch ID to the
microprocessor circuit via a digital interface.
The LED drive circuit interfaces with the microprocessor circuit via a
digital interface. The LED driver circuit is connected to the electronic
keypad via the electronic keypad ribbon cable. The LED driver circuit can
illuminate any combination of the electronic keypad LEDs. The LED driver
circuit also consists of three seven segment numerical LEDs which can be
made to display any three digit number.
The carriage position detection circuit consists of two mechanical lever
arm position switches, with one switch known as the pull stop switch, and
the other known as the push stop switch. The pull stop switch is located
on the end of the electronic assembly circuit board, furthest away from
the racket cradle, while the push stop switch is located on the opposite
end of the circuit board. The pull stop switch will be activated by the
snatch vise carriage assembly when the snatch vise carriage assembly
translates to a point furthest away from the racket cradle. The push stop
switch will be activated by the snatch vise carriage assembly when the
snatch vise carriage assembly translate to a point nearest the racket
cradle. The outputs of both the pull stop switch and the push stop switch
are connected directly to the microprocessor circuit.
The microprocessor circuit consists of a microprocessor and support
circuitry. The firmware, to run said microprocessor, resides within said
microprocessor.
The microprocessor receives the following inputs; user keypad information
via the keypad circuit, the bridge.sub.-- strain value from the bridge
strain gauge circuit, and the status of both the pull.sub.-- stop and
push.sub.-- stop switch status via the snatch vise position detector
circuit. The microprocessor has the following outputs; control of the gear
motor via the motor controller circuit, control of both the singular LEDs
and the seven segment numerical display.
Functional operation of the microprocessor circuit is controlled by the
onboard firmware where said firmware performs all of the before mentioned
functions of this electronic stringing device.
FIG. 7 shows the operational keypad. Power first applied to the present
device initiates a self-test verifying the operation of the strain gauges,
the motor drive screw assembly and the electronic controller assembly. The
machine sets itself to zero, essentially calibrating itself. If the test
is successful, the number 50.0 (pounds) or 22.7 (kilos) appears on the
display representing a commonly used tension. The operator uses the
up/down arrows to set his preferred tension if it is other than the
default.
To store a new tension, he touches the M1 button momentarily and waits for
a confirming beep and the lighting of an associated LED. Similarly he can
store a second preference in M2. With two tensions stored in memory the
operator has three tensions at his finger tips, M1, M2, and any other he
sets as displayed on the display.
Prior to stringing, the operator has other controls to consider. He may
choose to display the input tension in kilos rather than pounds. His
choice will be acknowledged with a beep and a lighted LED.
The Speed control allows the rate at which the motor control assembly
travels to be varied based on the operators preference after considering
the capability of the string and the racket.
The Count control allows for the display of the number of `pulls` or full
cycle repetitions of the vise since the machine was turned on and is
cumulative so long as power is on.
The Constant Pull control On/Off eliminates the enormous gap between
mechanical and electronic machines. Constant Pull Off replicates the
results of a traditional mechanical stringing machine wherein a brake is
applied when the dialed-in tension is reached. There is no further
movement of the vise even if the string looses elasticity and tension.
With Constant Pull On, if the device senses a loss of tension of more than
0.5 pounds it re-applies the dialed-in tension.
Tension settings and other controls are made by the operator and displayed
at the keypad. When the pulled string reaches the displayed tension, a
beep sounds to indicate success. If the vise reaches its furthest
extension yet has not tensioned the string as programmed, a series of
beeps indicates the string reached the pull stop switch and has not
reached the dialed-in tension.
Top